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hurd: Fix x86_64 _hurd_tls_fork

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It is illegal to call thread_get_state () on mach_thread_self (), so
this codepath cannot be used as-is to fork the calling thread's TLS.
Fortunately we can use THREAD_SELF (aka %fs:0x0) to find out the value
of our fs_base without calling into the kernel.

Fixes: f6cf701efc
"hurd: Implement TLS for x86_64"

Checked on x86_64-gnu: fork () now works!

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230517191436.73636-8-bugaevc@gmail.com>
This commit is contained in:
Sergey Bugaev 2023-05-17 22:14:33 +03:00 committed by Samuel Thibault
parent c7fcce38c8
commit 2f8ecb58a5
1 changed files with 19 additions and 6 deletions
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25
sysdeps/mach/hurd/x86_64/tls.h
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@ -140,12 +140,25 @@ _hurd_tls_fork (thread_t child, thread_t orig,
error_t err;
struct i386_fsgs_base_state state;
mach_msg_type_number_t state_count = i386_FSGS_BASE_STATE_COUNT;
err = __thread_get_state (orig, i386_FSGS_BASE_STATE,
(thread_state_t) &state,
&state_count);
if (err)
return err;
assert (state_count == i386_FSGS_BASE_STATE_COUNT);
extern thread_t hurd_thread_self (void);
if (orig != hurd_thread_self ())
{
err = __thread_get_state (orig, i386_FSGS_BASE_STATE,
(thread_state_t) &state,
&state_count);
if (err)
return err;
assert (state_count == i386_FSGS_BASE_STATE_COUNT);
}
else
{
/* It is illegal to call thread_get_state () on mach_thread_self ().
But we're only interested in the value of fs_base, and since we're
this thread, we know it points to our TCB. */
state.fs_base = (unsigned long) THREAD_SELF;
state.gs_base = 0;
}
return __thread_set_state (child, i386_FSGS_BASE_STATE,
(thread_state_t) &state,